Thread twisting



July 22, 1941. c. F. GRAM THREAD TWISTING 1940 2 Sheets-Sheet 1 FiledFeb. 19

jwue/Mm CARL 62AM al'tonuu July 22, 1941. c. F. GRAM 2,249,759

THREAD TWISTING Filed Feb. 19, 1940 2 Sheets-Shes; 2

CHAF GPA/v Gum M4 1 .direction, ,as' viewed from above.

Patented July 22, 1941 THREAD TWISTING Carl F. Gram, Elizabethton, Temp,assignor, to

North American Rayon Corporation, New York, N. Y., a corporation ofDelaware Application February 19,1940, Serial No. 319,774

17 Claims.

This invention relates to yarn twisting methods and apparatus, and inparticular to upstroke twisting of artificial filaments. 1

The upstroke twisting process is one in which the untwisted yarn is fedfrom a spool on a vertical revolving spindle, through a gathering guide,up and over a guide member, and on to a takeup spool which is rotatedabout a horizontal axis. Twisting takes place as the yarn in the form ofa balloon is rotated by the vertical spool and progresses linearly overthe guide member. A visualization of the twisting operation can beobtained by considering a vertical length of yarn which has its upperend restrained, as by the take-up spool, and its lower end turned aroundits own axis. The ballooning of the intermediate portion of the threadis due to the action of centrifugal force. Fundamentally, the sameoperation is reproduced when the upwardly traveling yarn is unwound fromthe vertical spool.

It has been found, however, that woven and dyed rayongoods produced fromyarn which has been twisted by the upstroke twisting process did notpossess the desired uniformity owing to physical irregularities ordefects in the twisted structure of the yarn. In the art, one of themost serious defects of this nature is known as corkscrews, and thesecorkscrews have been classified into several well defined types.

Before going into the classification of corkscrews, consideration willfirst be given to the frictional forces which produce them. A righthandor 8 twist is produced by turning the twisting spool to the right or ina counterclockwise With the ordinary ring guide, the guide may beconsidered as a straight rod tangential to the thread at the point ofcontact, since the guide radius is relatively large in comparison to theyarn in diameter. It will be apparent that the length of yarn betweenthe yarn supply spool and the guide is dependent upon the revolvingspeed of the balloon and the internal circumference of the guide.

From the standpoint of a single filament, the force L tends to drag thefilament downwardly with respect to the upwardly moving yarn body and toproduce an elongated length of filament due to the new and steeper angleof wind. This initial looseness of-the filament gives the force L animproved surface of attack on which it proceeds to continue strippingthis filament backwards (or preventing it from going forward, since itpiles up against the bottom of the guide) while duces the most markedirregularities in the finished dyed goods.

The lateral forces is responsible for a phaselagging of a singlefilament, but the filament so attacked tends to maintain approximatelythe same angle of wind. A slight extra length is made available,.andthis sometimes remains as a loosely wound, short filament loop. Thistype of defect is also a corkscrew, but of a more harmless variety. Itsmagnitude depends upon the duration of attack as well as upon the force.The forces L, S and R always act together and assist each other. Thusthe elimination of frictiona1 force L leaves only the type of corkscrewformed byfrictional force S. The corkscrews formed by thread guideshitherto employed in the turning, around its own axis with the samespeed of revolution as the balloon and with substantially the same speedas the spool. The first of these frictional forces, which will bedesignated L, is a linear one along the axis of the yarn and revolutionsof the yarn around its own axis. A--

third force acting'on "the thread or yarn is the result of the rotationof the thread within a cirart were always a result of fractional forcesS and L.

The corkscrew" which is due to relative longitudinal motion and thecorkscrew which results from relative lateral motion of the yarn endcome in contact with a portion of the guide which isspaced from thhethread or yarn. In

' other words, a zi-twist corkscrew may be procular or otherwise curvedthread guide. This latter force will be designated S, and is directlyduced' on an S twist thread. This type is fairly rare but producesserious defects such as slubs in the finished cloth.

There are then three common forms of corkscrews due to mechanical actionof the thread guide on the yarn, namely, a long form produced byrelative linear motion and in the direction of twist, another, butshorter, form due primarily to the relative lateral action of astationary encircling surface on the yarn, and the broken filament formwhich is folded back and wound in an opposite direction to the twist.The first and third forms are highly'objectionable because they resultin a thread having long constrictions causing thin places in the cloth,or slubs causing defects in the cloth.

Broadly, the purpose of the present invention is to improve the upstroketwisting process soas to eliminate loops or corkscrews and other similarirregularities.

More particularly, it is proposed to reduce substantially, or toeliminate completely, all damaging friction on the yarnbody while it isbeln guided during twisting.

From the apparatus standpoint, this invention contemplates a novel formof stationary helical thread guide.

Other detailed objects will appear in the ensuing description of thepreferred mode of practicing the method and the preferred forms ofapparatus.

In its broad method aspects, the invention comprises guiding the yarn insuch a manner that no relative longitudinal motion takes place betweenthe yarn and the guiding means. This is accomplished by providing ahelical guiding surfacewhose helix conforms to the natural helixformedby any point of the yarn as it is twisting-to gather the balloon and byproviding moving surfaces whose linear speed is equal to that of theyarn, at points where the use of a helical surface is not mechanicallypossible.

The novel apparatus includes in combination with a thread guidecomprising a relatively thin rod having a number ofhelical turns ofuniform pitch with a special or stabilizing bend leading thereto,another frictionless guide member in the form of a roller. Thestabilizing bend is for the purpose of preventing knocking of the yarnballoon on the support for the thread guide and for introducing the yarninto said guide with the minimum amount of friction.

Reference is now madeto the accompanying drawings, in which Fig. 1 is afront elevation of the essential parts of an upstroke twisting machine;

Fig. 2 is a side elevation of the same machine with certain parts shownin section;

Fig. 3 shows in plan view a preferred form of gathering guide;

Fig. 4 is a side elevation of the gathering guide V shown in-Fig. 3;

Fig. 5 is a plan view of a modified form of gathering guide; and v Fig.6 is a side elevation of the modified gathering guide of Fig. 5.

There is shown in Figs. 1 and 2 of the drawings, apparatus suitable foraccomplishing the novel method described herein. This apparatuscomprises, for purposes of illustration, the essential members of anupstroke twisting machine. A driven twisting spindle l0 verticallysupports a supply spool l2 having wound thereon a body of untwisted yarnI 4. In vertical alignment with the spindle In is a novel form of threadguide l6, which will be described with greater particularity at asubsequent point. The partially twisted yarn or thread l4- leaving theguide I6 is run over a guide member l8. illustrated as a groovedfrictionless roll having the outer extremity of its groove in verticalalignment with the center line of spindle Ill. The guide l6 andfrictionless roll I8 are supportedln spaced relation above the twistingspool I2 by a bra cket26 mounted on a fixed frame member 2l. After thethread l4 makes a nearly'right angle bend at the roll l8, it passesthrough a frictionless roller traverse guide which is attached to areciprocating traverse bar 24 supported for'movement' parallel to theaxis of a horizontal take-up spool 26. The

guide 22 includes two frictionless rollers 22a and 22b positionedparallel to each other and in spaced relation. The thread passes betweenthese rollers and. owing to the-free rotatable movement of the rollers,nofriction is, produced upon contact of the thread with either one ofthe rollers.

As is customary in such machines, the traverse bar 24 is suitablyreciprocated by a mechanism which is not shown, and the take-up spool 26is rotated in the direction indicated'in Fig. 2 by a pair of frictiondrive rollers 28 rotating with a driven shaft 30. A pair of groovedrollers 32 enand gathered by the thread guide l6.and guide roll 18. Fromwhat has beensaid, it will be understood that the twist per unit oflength which is given to the yarn by the twisting apparatus depends uponthe linear rate of advance of the yarn, or the take-up speed, and therevolutions per unit time of the twisting spool I2. By way of example, atake-up speed of 2,000 inches per minute and a twisting spool speed of6,000 revolutions per minute will be assumed. Under these conditions,the yarn will be given a twist of three revolutions or turns per inch.As previously explained, the direction of'twist is determined by thedirection of rotation of the twisting spool l2. Every point of a threadso twisted describes a spiralwhich has a lead of one 'third inch, alongthe path of the thread. When it is desired to give the yarn for example5 turns per inch, the lead of the spiral will be one-fifth inch.

etc. In other words there is a distinct relation between the number ofturns per inch put into the yarn, and the lead of the helix of thethread guide since the lead will be made thereciprocal value of theaverage number of turns twist to be imparted to the yarn. Expressedmathematically where l is lead and where n is the number of' turns twistper unit length. It is to be understood that lead means the progress ofthe yarn of that path, in one revolution.

The character of the thread guide l6 of this invention is determined bythe direction and number of turns per inch which it is desired to impartto the yarn. This is in sharp distinction to the previous practice ofusing a simple ring or random pigtail.

Since the guides l6 and I60, which are illustrated in Figs. 3, 4, 5 and6, are intended for producing three right-hand or 8 turns per inch, the

along its path, regardless of change of direction I helical portions areof uniform lead, one-third inch, and comprise one and one-quarter turns,with the upper end terminating on the helix. The turns of each helix areright turns in that they progress upwardly and to the right, as seen inthe elevations of Figs. 4 and 6. A minimum number of turns necessary toguide the yarn in its natural spiral path is used, in order that thetime of contact can be made as short as possible. When the yarn is beinggiven three turns per inch, it will contact theinside of the helixportion of this guide only at longitudinally spaced points which areone-third of an inch apart. The intermediate points will not contact thehelix of the guide, nor be subjected to the laterally frictional forcestherein. Each succeeding one-third inch length of yarn will progressupwardly through the guide in the samemanner. .Guides I6 and I 60 havehelix portions with internal diameters of approximately one-quarterinch, a practical minimum being used for its effect on the lateral forceS, holding the internal circumference to a minimum length. I

Where the term number has been used with respect to the helical turnsof. the guides I 6 and I60, it is intended to mean one or more. Whilethe irreducible minimum in practice appears to be one and a fraction,one and one-quarter turns being now preferred, it must be realized thata plurality of whole turns may occasionally be found advantageous.

By guiding a thread in this manner substantially, all relativelongitudinal motion between the threacl and its guide will beeliminated, and the lesser frictional forces which have been denoted Sand R will be greatly reduced by th nature and limited extent ofcontact.

Reference is now made to the horizontal, extended portion .or supportIT, or Ill, which forms a part of the illustrated guides. When thesupport portion is connected directly to the bottom of the helix portionor projects straight and radially as a continuation thereof, it has beenfound to interfere with the balloon and to provide another serioussource of both longitudinal and lateral friction. To eliminate thisfriction source and further to improve th quality and uniformity of thetwistedyarn a bal- Icon-stabilizer or stabilizing bend was evolved.

The first approach to this problem of balloon" interference or knockingagainst the guide supporting rod (H or MI) was to add an extra halfloopI9l to the bottom of the helical spiral. This half-loop is of a largermean diameter than the helical portion and is located eccentrically withrespect to the vertical axis thereof. It is disposed so as to ensnarethe yarn balloon 180 degrees ahead of the supporting rod Ill and topress it gently downward in such a manner that the free part of theballoon will swing out below the supporting rod and thus clear it. Afurther function of the stabilizer loop is to engage that point of thethread which will contact the helical spiral a half-revolution later.The locus of this point can be determined geometrically, and thehalf-loop I9I is so shaped that the approaching yarn point will travelin constant contact with it and thus be free from linear friction.

The stabilizer bend (l9 or ISI) may be compared with a true spiral ofArchimedes of which it is an adaptation. It has, therefore, a constantrate of approach radially toward the helix porti n of th guide (I6 orI60) The fundamental feature of the helical guide is e ended to thedicate that very slight longitudinal relative mostabilizer bendbydistorting the Archimedes spiral into a three-dimensional convolutionwhich is semi-circular in plan and has every point on its yarn contactsurface or its center line a constant distance (the lead of' the helix,namely, one-third inch) from the yarn contact surface or center line ofthe lower-most and closest helix tum.

A, further development of the guide consists in extending the half-loopstabilizer into a full horizontal loop I9 for 315 degrees around theaxis of. the vertical spiral guide, maintaining the principle of thespiral ofArchimedes, and continuing this spiral tangentially radiallythereafter to form an integral supporting rod I! for the entire threadguide I6. This is the preferred embodiment shown in Figs. 3 and 4, andin which the guide is self-threading and balloon-retaining. Without thefull loop IS the balloon may sometimes run out of the guide withdamaging results to the yarn.

For all practical purposes, the inner 180 degrees of the full stabilizerloop I9 or the halfloop l9l may be shaped so as to lie in two planeswhich intersect midway around, that is, the degree point. Figs. 3, 4, 5,and 6 are illustrative of this more easily bent and practical form.

- The herein disclosed method and the preferred embodiment of apparatusfor practicing that method afford a simple and accurate control of theupstroke twisting operation. In the case of artificial yarns'such asrayon, they produce a uniform thread which is substantially free fromtwisting defects having the nature of corkscrews, and loops. Principleshave been established which are applicable to any similar problem ofguiding a thread for twisting.

The apparatus which has been described represents the presentlypreferred means of accomplishing the twisting operation, and ischaracterized by a definite relationship between the direction and pitchof the thread ,guide and the degree of twist imposed upon the thread oryarn. Novel and efllcient means in the form of a stabilizing loop hasbeen devised for introducing the yarn into the thread guide Withoutcausing any undesired relative motion.

Through the medium of this invention rayon goods can be greatly improvedin quality without departing from the normal production twisting speedsof 5,000 revolutions per minute and upward. Extensive tests havedemonstrated that commercially corkscrew-free twisted yarn can beproduced in upstroke twisting at high speeds.

It should be understood that the foregoing exemplifications of thepresent invention in its application to the specified operations aresimply illustrative of various similar applications of the inventioninvolving the principles herein set forth. Modifications and variationsof this invention will readily be recognized in the art, and it isdesired to include all modifications and variations coming within thescope of the appended claims. In these claims the terms substantial andsubstantially" respectively are used to intions may occur which,however, are of a magnitude insuflicient to detrimentally affect thetextile qualities of the twisted yarns.

I claim:

1. That improvement in upstroke twisting which comprises leading a yarnover guiding means without substantial relative longitudinal motionbetween any point on the yarn and the guiding means While the yarn is incontact with the guiding means and is being twisted.

2. That improvement in upstroke twisting of a yarn which comprisesguiding the yarn over a spiral guide surface having substantially thesame lead and direction as the natural helical path described in spaceby any point on the yarn while it is being guided.

3. That improvement in upstroke twisting which comprises guiding theyarn by means of a spiral guide the lead of which is the reciprocalvalue of the average number of turns twist imparted to the yarn and thedirection of which is the same as that of the natural helix described inspace by any point on the travelingyam.

4. A method of substantially eliminating relative longitudinal motionbetween any point on a yarn and the guide in upstroke twisting whichincludes the step of supporting spaced points on the yarn by. means of aspiral guide whose spiral corresponds to the natural spiral described inspace in the guiding region by any point on the traveling yarn.

5. A method of substantially eliminating relative longitudinal motionbetween a yarn and its guide in upstroke twisting which includes thestep of guiding the yarn by a stationary spiral surface whichcorresponds in shape to the natural spiral described in space by anypoint on the yarn in the guiding region during the upstroke twistingoperation.

6. A method of substantially eliminating relative longitudinal motionand minimizing relative lateral motion between a yarn and its guide inupstroke twisting which includes the step of supporting only constantlyspaced points on the yarn in a spiral path which corresponds to thenatural spiral described in space by any point on the yarn in theguiding region during the upstroke twisting operation.

7. A thread guide comprising a rod having a number of helical turns ofuniform pitch and a stabilizing bend leading thereto, said stabilizingbend having the shape of a spiral of Archimedes which has been modifiedin elevation so that every point thereon is substantially equidistant inspace from the nearest portion of the closest helical turn.

8.- A thread guide comprising a rod having a number of helical turns ofuniform pitch and a full-loop stabilizer leading thereto, saidstabilizer having the shape of a spiral of Archimedes which has beenmodified in elevation so that every point thereon is substantiallyequidistant in space from the nearest portion of the closest helicalturn.

9. A thread guide consisting of a rod having a number of helical turnsof uniform pitch and a full-loop stabilizer leading thereto, saidstabilizer having the shape of a spiral of Archimedes which has beenmodified in elevation so that every point thereon is substantiallyequidistant in space from the nearest portion of the closest helicalturn, the stabilizer having a supporting portion extending from itsouter end.

10. A thread guidecomprising a rod having a number of helical turns ofImiform pitch and a half-loop stabilizer leading thereto, saidstabilizer having the shape of a spiral of Archimedes which has beenmodified in elevation so that every point thereon is substantiallyequidistant in space from the nearest portion of the closest helicalturn.

11. A thread guide comprising a relatively thin and smooth, circular rodhaving a number of helical turns of uniform pitch and an outwardlyspaced stabilizing bend leading thereto, said stabilizing bend havingapproximately the shape of a spiral of Archimedes.

12. A thread guide comprising a polished, stainless steel rod having anumber of helical turns of uniform pitch and a stabilizing bend leadingthereto, said stabilizing bend having the shape of a spiral with anapproximately constant rate of approach radially toward the axis of thehelical turns.

13. A self-threading thread guide consisting of a rod having a smallnumber of helical turns of uniform pitch, a full-tum stabilizing bendleading thereto. and an extended supporting portion projecting from theouter end of the stabilizing bend, said stabilizing bend having theshape of a spiral of Archimedes which has been modified in elevation sothat every point thereon is substantially equidistant in space from thenearest portion of the closest helical turn.

14. Thread guiding means comprising a contlnuous spiral surface forsupporting longitudinally spaced points on a thread, said surface havinga helical portion of uniform pitch and a portion leading thereto whichhas an approximately constant rate of approach radially toward the axisof the helical portion for preventing interference and friction as thethread enters the guiding means.

15. Thread guiding meanscomprising a continuous, curved surface forsupporting longitudinally spaced points on a thread, said surface havinga helical guide portion of uniform pitch and a spiral portion of greatermean diameter than the helical portion leading thereto for threading theguide portion.

16. In an upstroke spinning apparatus, a twisting spool, a spiral threadguide spaced above said spool with its axis concentric therewith, and africtionless guide disposed above the helical guide and in alignmentwith thespool and said helical guide for changing the direction of anupwardly moving thread and serving as a point about which twisting takesplace, said spiral thread guide having a numben of helical turns ofuniform pitch and a spiral stabilizer bend of greater mean diameter thanthe helical turns for threading the 1 guide.

17. In an upstroke spinning apparatus, a twisting spool, a spiral threadguide spaced above said spool with its axis concentric therewith, and africtionless roller disposed above the helical guide prising a number ofvertical helical turns of uniform pitch surmounting a stabilizing bendhaving the shape of a spiral of Archimedes distorted in elevation sothat every point thereon is approximately equidistant in space from thenearest portion of the closest helical turn.

' CARL F. GRAM.

Certificate of Correction Patent No. 2,249,759. July 22, 1941.

CARL F. GRAM It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Page 2, second column, line 60,

for i=5 read Z=%; and that the said Letters Patent should be read withthis correction therein that the same may conform to the record of thecase in the Patent Oflice.

Signed and sealed this 24th day of March, A. D. 1942.

[SEAL] HENRY VAN ARSDALE,

Acting Commissioner of Patents.

